Fluid flow patterns, pilot study

Glaser and Litt (G4) have proposed, in an extension of the above study, a model for gas-liquid flow through a b d of porous particles. The bed is assumed to consist of two basic structures which influence the fluid flow patterns (1) Void channels external to the packing, with which are associated dead-ended pockets that can hold stagnant pools of liquid and (2) pore channels and pockets, i.e., continuous and dead-ended pockets in the interior of the particles. On this basis, a theoretical model of liquid-phase dispersion in mixed-phase flow is developed. The model uses three bed parameters for the description of axial dispersion (1) Dispersion due to the mixing of streams from various channels of different residence times (2) dispersion from axial diffusion in the void channels and (3) dispersion from diffusion into the pores. The model is not applicable to turbulent flow nor to such low flow rates that molecular diffusion is comparable to Taylor diffusion. The latter region is unlikely to be of practical interest. The model predicts that the reciprocal Peclet number should be directly proportional to nominal liquid velocity, a prediction that has been confirmed by a few determinations of residence-time distribution for a wax desulfurization pilot reactor of 1-in. diameter packed with 10-14 mesh particles. 

An interwell chemical tracer study established fluid flow patterns within the pilot. Decline curve analysis showed that TFSA injection recovered more than 8150 +... 

To establish the well drainage boundaries and fluid flow patterns within the TFSA-waterflood pilot, an interwell chemical tracer study was conducted. Sodium thiocyanate was selected as the tracer on the basis of its low adsorption characteristics on reservoir rocks (36-38), its low and constant background concentration (0.9 mg/kg) in produced fluids and its ease and accuracy of analysis(39). On July 8, 1986, 500 lb (227 kg) of sodium thiocyanate dissolved in 500 gal (1.89 m3> of injection brine (76700 mg/kg of thiocyanate ion) were injected into Well TU-120. For the next five months, samples of produced fluids were obtained three times per week from each production well. The thiocyanate concentration in the produced brine samples were analyzed in duplicate by the standard ferric nitrate method(39) and in all cases, the precision of the thiocyanate determinations were within 0.3 mg/kg. The concentration of the ion in the produced brine returned to background levels when the sampling and analysis was concluded. 

Table IV. Tracer Study Established Fluid Flow Patterns Within the Pilot Area...

Fluid flow patterns within the pilot pattern were characterized by an interwell chemical tracer study which showed that as much as 38.4 % of the fluids injected into the pilot flowed out of the unconfined pattern and 75.9 % of the produced fluids are from outside the pattern. 

The next-best option is the use of a pilot-scale model of the fiber. Here the fluid flow patterns at the sur ce of the medium will, at least, be similar to the large-scale luut. The pilot fiber cannot produce information on wear properties, e.g. produced by the effect of movement of large, heavy plates. Cloth behaviour must at least be studied e q)erimentally using laboratory Buchner fibers. The latter low-pressure test units will provide information on the resistance of the used medium, tendency to blind, etc. However, the fibration process conducted downwards on the sur ce of the medium, imder a pressure differential of 0.5 bar, cannot be expected to simulate exactly the processes occurring inside large recessed-p te or plate and fi ame fibers where particle movement is a complex mixture in vertical and horizontal directions. 

TFSA-WATERFLOOD PILOT. A 36 acre (1.14 x lO m2) TFSA-waterflood pilot was recently conducted in the Torrance Field in the Los Angeles Basin of Southern California. To characterize the fluid floi patterns within the pilot, an interwell chemical tracer study was conducted with sodium thiocyanate. Results of the tracer study are shown in Table IV. Only 61.6 % of the injected tracer was recovered in the produced fluids, indicating that as much as 38.4 % of the injected fluids were flowing out of the pattern. Furthermore, since only 1604 bbl/d (255 m3/d) of brine was injected into the pattern, as much as 75.9 % of the total fluids produced by pilot wells were from outside the pattern. 

In the first case, the minimum values for the economic yardsticks were evaluated assuming that a conservative 7300 bbl (= 8150 bbl -850 bbl 1160 m3 = 1295 m3 - 135 m3) of incremental oil had been produced by the end of the project. Maximum values for the economic data were calculated by assuming that 9000 bbl (= 8150 bbl + 850 bbl 1430 m3 = 1295 m3 + 135 m3) of incremental oil were produced by only 61.6 % of the TFSA which had been injected into Well TU-120 this assumption is based on the results of the tracer study which showed that as much as 38.4 % of the injected fluids flowed out of the pilot pattern. In the final case, the most probable values for the economic yardsticks were calculated assuming the 8150 bbl (1295 m3> of incremental oil were produced by 90 % of the TFSA. 

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